Not allow ON DELETE/UPDATE SET DEFAULT actions on columns that default to sequences (#6340)

Given that we drop DEFAULT nextval('sequence') expressions from
shard relation columns, allowing `ON DELETE/UPDATE SET DEFAULT`
on such columns might cause inserting NULL values as a result
of a delete/update operation.

For this reason, we disallow ON DELETE/UPDATE SET DEFAULT actions
on columns that default to sequences.

DESCRIPTION: Disallows having ON DELETE/UPDATE SET DEFAULT actions on
columns that default to sequences

Fixes #6339.

(cherry picked from commit a868cc049a)

 Conflicts (dropped those changes since pg15 is not supported on 11.0):
	src/test/regress/expected/pg15.out
	src/test/regress/sql/pg15.sql

src/backend/distributed/commands/foreign_constraint.c

@@ -23,6 +23,7 @@
 #include "catalog/pg_type.h"
 #include "distributed/colocation_utils.h"
 #include "distributed/commands.h"
+#include "distributed/commands/sequence.h"
 #include "distributed/coordinator_protocol.h"
 #include "distributed/listutils.h"
 #include "distributed/coordinator_protocol.h"
@@ -30,6 +31,7 @@
 #include "distributed/namespace_utils.h"
 #include "distributed/reference_table_utils.h"
 #include "distributed/version_compat.h"
+#include "distributed/worker_protocol.h"
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
 #include "utils/inval.h"
@@ -56,6 +58,8 @@ typedef bool (*CheckRelationFunc)(Oid);
 /* Local functions forward declarations */
 static void EnsureReferencingTableNotReplicated(Oid referencingTableId);
 static void EnsureSupportedFKeyOnDistKey(Form_pg_constraint constraintForm);
+static bool ForeignKeySetsNextValColumnToDefault(HeapTuple pgConstraintTuple);
+static List * ForeignKeyGetDefaultingAttrs(HeapTuple pgConstraintTuple);
 static void EnsureSupportedFKeyBetweenCitusLocalAndRefTable(Form_pg_constraint
 															constraintForm,
 															char
@@ -196,6 +200,23 @@ ErrorIfUnsupportedForeignConstraintExists(Relation relation, char referencingDis
 			referencedReplicationModel = referencingReplicationModel;
 		}
 
+		/*
+		 * Given that we drop DEFAULT nextval('sequence') expressions from
+		 * shard relation columns, allowing ON DELETE/UPDATE SET DEFAULT
+		 * on such columns causes inserting NULL values to referencing relation
+		 * as a result of a delete/update operation on referenced relation.
+		 *
+		 * For this reason, we disallow ON DELETE/UPDATE SET DEFAULT actions
+		 * on columns that default to sequences.
+		 */
+		if (ForeignKeySetsNextValColumnToDefault(heapTuple))
+		{
+			ereport(ERROR, (errmsg("cannot create foreign key constraint "
+								   "since Citus does not support ON DELETE "
+								   "/ UPDATE SET DEFAULT actions on the "
+								   "columns that default to sequences")));
+		}
+
 		bool referencingIsCitusLocalOrRefTable =
 			(referencingDistMethod == DISTRIBUTE_BY_NONE);
 		bool referencedIsCitusLocalOrRefTable =
@@ -298,6 +319,104 @@ ErrorIfUnsupportedForeignConstraintExists(Relation relation, char referencingDis
 }
 
 
+/*
+ * ForeignKeySetsNextValColumnToDefault returns true if at least one of the
+ * columns specified in ON DELETE / UPDATE SET DEFAULT clauses default to
+ * nextval().
+ */
+static bool
+ForeignKeySetsNextValColumnToDefault(HeapTuple pgConstraintTuple)
+{
+	Form_pg_constraint pgConstraintForm =
+		(Form_pg_constraint) GETSTRUCT(pgConstraintTuple);
+
+	List *setDefaultAttrs = ForeignKeyGetDefaultingAttrs(pgConstraintTuple);
+	AttrNumber setDefaultAttr = InvalidAttrNumber;
+	foreach_int(setDefaultAttr, setDefaultAttrs)
+	{
+		if (ColumnDefaultsToNextVal(pgConstraintForm->conrelid, setDefaultAttr))
+		{
+			return true;
+		}
+	}
+
+	return false;
+}
+
+
+/*
+ * ForeignKeyGetDefaultingAttrs returns a list of AttrNumbers
+ * might be set to default ON DELETE or ON UPDATE.
+ *
+ * For example; if the foreign key has SET DEFAULT clause for
+ * both actions, then returns a superset of the attributes that
+ * might be set to DEFAULT on either of those actions.
+ */
+static List *
+ForeignKeyGetDefaultingAttrs(HeapTuple pgConstraintTuple)
+{
+	bool isNull = false;
+	Datum referencingColumnsDatum = SysCacheGetAttr(CONSTROID, pgConstraintTuple,
+													Anum_pg_constraint_conkey, &isNull);
+	if (isNull)
+	{
+		ereport(ERROR, (errmsg("got NULL conkey from catalog")));
+	}
+
+	List *referencingColumns =
+		IntegerArrayTypeToList(DatumGetArrayTypeP(referencingColumnsDatum));
+
+	Form_pg_constraint pgConstraintForm =
+		(Form_pg_constraint) GETSTRUCT(pgConstraintTuple);
+	if (pgConstraintForm->confupdtype == FKCONSTR_ACTION_SETDEFAULT)
+	{
+		/*
+		 * Postgres doesn't allow specifying SET DEFAULT for a subset of
+		 * the referencing columns for ON UPDATE action, so in that case
+		 * we return all referencing columns regardless of what ON DELETE
+		 * action says.
+		 */
+		return referencingColumns;
+	}
+
+	if (pgConstraintForm->confdeltype != FKCONSTR_ACTION_SETDEFAULT)
+	{
+		return NIL;
+	}
+
+	List *onDeleteSetDefColumnList = NIL;
+#if PG_VERSION_NUM >= PG_VERSION_15
+	Datum onDeleteSetDefColumnsDatum = SysCacheGetAttr(CONSTROID, pgConstraintTuple,
+													   Anum_pg_constraint_confdelsetcols,
+													   &isNull);
+
+	/*
+	 * confdelsetcols being NULL means that "ON DELETE SET DEFAULT" doesn't
+	 * specify which subset of columns should be set to DEFAULT, so fetching
+	 * NULL from the catalog is also possible.
+	 */
+	if (!isNull)
+	{
+		onDeleteSetDefColumnList =
+			IntegerArrayTypeToList(DatumGetArrayTypeP(onDeleteSetDefColumnsDatum));
+	}
+#endif
+
+	if (list_length(onDeleteSetDefColumnList) == 0)
+	{
+		/*
+		 * That means that all referencing columns need to be set to
+		 * DEFAULT.
+		 */
+		return referencingColumns;
+	}
+	else
+	{
+		return onDeleteSetDefColumnList;
+	}
+}
+
+
 /*
  * EnsureSupportedFKeyBetweenCitusLocalAndRefTable is a helper function that
  * takes a foreign key constraint form for a foreign key between two citus

src/test/regress/expected/multi_foreign_key.out

@@ -1172,5 +1172,108 @@ SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
 
 (1 row)
 
+CREATE TABLE set_on_default_test_referenced(
+    col_1 int, col_2 int, col_3 int, col_4 int,
+    unique (col_1, col_3)
+);
+SELECT create_reference_table('set_on_default_test_referenced');
+ create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int, col_2 int, col_3 serial, col_4 int,
+    FOREIGN KEY(col_1, col_3)
+    REFERENCES set_on_default_test_referenced(col_1, col_3)
+    ON UPDATE SET DEFAULT
+);
+-- from distributed / reference to reference, fkey exists before calling the UDFs
+SELECT create_distributed_table('set_on_default_test_referencing', 'col_1');
+ERROR:  cannot create foreign key constraint since Citus does not support ON DELETE / UPDATE SET DEFAULT actions on the columns that default to sequences
+SELECT create_reference_table('set_on_default_test_referencing');
+ERROR:  cannot create foreign key constraint since Citus does not support ON DELETE / UPDATE SET DEFAULT actions on the columns that default to sequences
+DROP TABLE set_on_default_test_referencing;
+CREATE TABLE set_on_default_test_referencing(
+    col_1 serial, col_2 int, col_3 int, col_4 int
+);
+SELECT create_reference_table('set_on_default_test_referencing');
+ create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- from reference to reference, fkey doesn't exist before calling the UDFs
+ALTER TABLE set_on_default_test_referencing ADD CONSTRAINT fkey
+FOREIGN KEY(col_1, col_3) REFERENCES set_on_default_test_referenced(col_1, col_3)
+ON DELETE SET DEFAULT;
+ERROR:  cannot create foreign key constraint since Citus does not support ON DELETE / UPDATE SET DEFAULT actions on the columns that default to sequences
+DROP TABLE set_on_default_test_referencing;
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int, col_2 serial, col_3 int, col_4 bigserial
+);
+SELECT create_reference_table('set_on_default_test_referencing');
+ create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- ok since referencing columns are not based on sequences
+ALTER TABLE set_on_default_test_referencing ADD CONSTRAINT fkey
+FOREIGN KEY(col_1, col_3) REFERENCES set_on_default_test_referenced(col_1, col_3)
+ON DELETE SET DEFAULT;
+DROP TABLE set_on_default_test_referencing;
+CREATE SEQUENCE test_sequence;
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int, col_2 int, col_3 int DEFAULT nextval('test_sequence'), col_4 int
+);
+SELECT create_distributed_table('set_on_default_test_referencing', 'col_1');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- from distributed to reference, fkey doesn't exist before calling the UDFs
+ALTER TABLE set_on_default_test_referencing ADD CONSTRAINT fkey
+FOREIGN KEY(col_1, col_3) REFERENCES set_on_default_test_referenced(col_1, col_3)
+ON DELETE SET DEFAULT ON UPDATE SET DEFAULT;
+ERROR:  cannot create foreign key constraint since Citus does not support ON DELETE / UPDATE SET DEFAULT actions on the columns that default to sequences
+DROP TABLE set_on_default_test_referenced;
+CREATE TABLE set_on_default_test_referenced(
+    col_1 int, col_2 int, col_3 int, col_4 int,
+    unique (col_1, col_3)
+);
+SELECT create_distributed_table('set_on_default_test_referenced', 'col_1');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+DROP TABLE set_on_default_test_referencing;
+CREATE TABLE set_on_default_test_referencing(
+    col_1 bigserial, col_2 int, col_3 int DEFAULT nextval('test_sequence'), col_4 int,
+    FOREIGN KEY(col_1, col_3)
+    REFERENCES set_on_default_test_referenced(col_1, col_3)
+    ON DELETE SET DEFAULT
+);
+-- from distributed to distributed, fkey exists before calling the UDFs
+SELECT create_distributed_table('set_on_default_test_referencing', 'col_1');
+ERROR:  cannot create foreign key constraint since Citus does not support ON DELETE / UPDATE SET DEFAULT actions on the columns that default to sequences
+DROP TABLE set_on_default_test_referencing;
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int DEFAULT nextval('test_sequence'), col_2 int, col_3 int, col_4 int
+);
+SELECT create_distributed_table('set_on_default_test_referencing', 'col_1');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- from distributed to distributed, fkey doesn't exist before calling the UDFs
+ALTER TABLE set_on_default_test_referencing ADD CONSTRAINT fkey
+FOREIGN KEY(col_1, col_3) REFERENCES set_on_default_test_referenced(col_1, col_3)
+ON DELETE SET DEFAULT;
+ERROR:  cannot create foreign key constraint since Citus does not support ON DELETE / UPDATE SET DEFAULT actions on the columns that default to sequences
 -- we no longer need those tables
-DROP TABLE referenced_by_reference_table, references_to_reference_table, reference_table, reference_table_second, referenced_local_table, self_referencing_reference_table, dropfkeytest2;
+DROP TABLE referenced_by_reference_table, references_to_reference_table, reference_table, reference_table_second, referenced_local_table, self_referencing_reference_table, dropfkeytest2,
+           set_on_default_test_referenced, set_on_default_test_referencing;

src/test/regress/expected/ref_citus_local_fkeys.out

@@ -250,6 +250,52 @@ BEGIN;
 	CREATE TABLE referencing_table(id int, ref_id int, FOREIGN KEY(ref_id) REFERENCES referenced_table(id) ON DELETE SET DEFAULT);
 ERROR:  cannot switch local execution status from local execution disabled to local execution enabled since it can cause visibility problems in the current transaction
 ROLLBACK;
+CREATE TABLE set_on_default_test_referenced(
+    col_1 int, col_2 int, col_3 int, col_4 int,
+    unique (col_1, col_3)
+);
+SELECT create_reference_table('set_on_default_test_referenced');
+ create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- from citus local to reference - 1
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int, col_2 int, col_3 serial, col_4 int,
+    FOREIGN KEY(col_1, col_3)
+    REFERENCES set_on_default_test_referenced(col_1, col_3)
+    ON UPDATE SET DEFAULT
+);
+ERROR:  cannot create foreign key constraint since Citus does not support ON DELETE / UPDATE SET DEFAULT actions on the columns that default to sequences
+CREATE TABLE set_on_default_test_referencing(
+    col_1 serial, col_2 int, col_3 int, col_4 int
+);
+-- from citus local to reference - 2
+ALTER TABLE set_on_default_test_referencing ADD CONSTRAINT fkey
+FOREIGN KEY(col_1, col_3) REFERENCES set_on_default_test_referenced(col_1, col_3)
+ON DELETE SET DEFAULT;
+ERROR:  cannot create foreign key constraint since Citus does not support ON DELETE / UPDATE SET DEFAULT actions on the columns that default to sequences
+DROP TABLE set_on_default_test_referencing, set_on_default_test_referenced;
+NOTICE:  executing the command locally: DROP TABLE IF EXISTS ref_citus_local_fkeys.set_on_default_test_referenced_xxxxx CASCADE
+CREATE TABLE set_on_default_test_referenced(
+    col_1 int, col_2 int, col_3 int, col_4 int,
+    unique (col_1, col_3)
+);
+SELECT citus_add_local_table_to_metadata('set_on_default_test_referenced');
+ citus_add_local_table_to_metadata
+---------------------------------------------------------------------
+
+(1 row)
+
+-- from citus local to citus local
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int, col_2 int, col_3 serial, col_4 int,
+    FOREIGN KEY(col_1, col_3)
+    REFERENCES set_on_default_test_referenced(col_1, col_3)
+    ON DELETE SET DEFAULT
+);
+ERROR:  cannot create foreign key constraint since Citus does not support ON DELETE / UPDATE SET DEFAULT actions on the columns that default to sequences
 -- cleanup at exit
 DROP SCHEMA ref_citus_local_fkeys CASCADE;
-NOTICE:  drop cascades to 6 other objects
+NOTICE:  drop cascades to 8 other objects

src/test/regress/sql/multi_foreign_key.sql

@@ -696,5 +696,87 @@ DROP TABLE dropfkeytest1 CASCADE;
 -- this should work
 SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
 
+CREATE TABLE set_on_default_test_referenced(
+    col_1 int, col_2 int, col_3 int, col_4 int,
+    unique (col_1, col_3)
+);
+SELECT create_reference_table('set_on_default_test_referenced');
+
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int, col_2 int, col_3 serial, col_4 int,
+    FOREIGN KEY(col_1, col_3)
+    REFERENCES set_on_default_test_referenced(col_1, col_3)
+    ON UPDATE SET DEFAULT
+);
+
+-- from distributed / reference to reference, fkey exists before calling the UDFs
+SELECT create_distributed_table('set_on_default_test_referencing', 'col_1');
+SELECT create_reference_table('set_on_default_test_referencing');
+
+DROP TABLE set_on_default_test_referencing;
+CREATE TABLE set_on_default_test_referencing(
+    col_1 serial, col_2 int, col_3 int, col_4 int
+);
+SELECT create_reference_table('set_on_default_test_referencing');
+
+-- from reference to reference, fkey doesn't exist before calling the UDFs
+ALTER TABLE set_on_default_test_referencing ADD CONSTRAINT fkey
+FOREIGN KEY(col_1, col_3) REFERENCES set_on_default_test_referenced(col_1, col_3)
+ON DELETE SET DEFAULT;
+
+DROP TABLE set_on_default_test_referencing;
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int, col_2 serial, col_3 int, col_4 bigserial
+);
+SELECT create_reference_table('set_on_default_test_referencing');
+
+-- ok since referencing columns are not based on sequences
+ALTER TABLE set_on_default_test_referencing ADD CONSTRAINT fkey
+FOREIGN KEY(col_1, col_3) REFERENCES set_on_default_test_referenced(col_1, col_3)
+ON DELETE SET DEFAULT;
+
+DROP TABLE set_on_default_test_referencing;
+
+CREATE SEQUENCE test_sequence;
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int, col_2 int, col_3 int DEFAULT nextval('test_sequence'), col_4 int
+);
+SELECT create_distributed_table('set_on_default_test_referencing', 'col_1');
+
+-- from distributed to reference, fkey doesn't exist before calling the UDFs
+ALTER TABLE set_on_default_test_referencing ADD CONSTRAINT fkey
+FOREIGN KEY(col_1, col_3) REFERENCES set_on_default_test_referenced(col_1, col_3)
+ON DELETE SET DEFAULT ON UPDATE SET DEFAULT;
+
+DROP TABLE set_on_default_test_referenced;
+CREATE TABLE set_on_default_test_referenced(
+    col_1 int, col_2 int, col_3 int, col_4 int,
+    unique (col_1, col_3)
+);
+SELECT create_distributed_table('set_on_default_test_referenced', 'col_1');
+
+DROP TABLE set_on_default_test_referencing;
+CREATE TABLE set_on_default_test_referencing(
+    col_1 bigserial, col_2 int, col_3 int DEFAULT nextval('test_sequence'), col_4 int,
+    FOREIGN KEY(col_1, col_3)
+    REFERENCES set_on_default_test_referenced(col_1, col_3)
+    ON DELETE SET DEFAULT
+);
+
+-- from distributed to distributed, fkey exists before calling the UDFs
+SELECT create_distributed_table('set_on_default_test_referencing', 'col_1');
+
+DROP TABLE set_on_default_test_referencing;
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int DEFAULT nextval('test_sequence'), col_2 int, col_3 int, col_4 int
+);
+SELECT create_distributed_table('set_on_default_test_referencing', 'col_1');
+
+-- from distributed to distributed, fkey doesn't exist before calling the UDFs
+ALTER TABLE set_on_default_test_referencing ADD CONSTRAINT fkey
+FOREIGN KEY(col_1, col_3) REFERENCES set_on_default_test_referenced(col_1, col_3)
+ON DELETE SET DEFAULT;
+
 -- we no longer need those tables
-DROP TABLE referenced_by_reference_table, references_to_reference_table, reference_table, reference_table_second, referenced_local_table, self_referencing_reference_table, dropfkeytest2;
+DROP TABLE referenced_by_reference_table, references_to_reference_table, reference_table, reference_table_second, referenced_local_table, self_referencing_reference_table, dropfkeytest2,
+           set_on_default_test_referenced, set_on_default_test_referencing;

src/test/regress/sql/ref_citus_local_fkeys.sql

@@ -159,5 +159,44 @@ BEGIN;
 	CREATE TABLE referencing_table(id int, ref_id int, FOREIGN KEY(ref_id) REFERENCES referenced_table(id) ON DELETE SET DEFAULT);
 ROLLBACK;
 
+CREATE TABLE set_on_default_test_referenced(
+    col_1 int, col_2 int, col_3 int, col_4 int,
+    unique (col_1, col_3)
+);
+SELECT create_reference_table('set_on_default_test_referenced');
+
+-- from citus local to reference - 1
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int, col_2 int, col_3 serial, col_4 int,
+    FOREIGN KEY(col_1, col_3)
+    REFERENCES set_on_default_test_referenced(col_1, col_3)
+    ON UPDATE SET DEFAULT
+);
+
+CREATE TABLE set_on_default_test_referencing(
+    col_1 serial, col_2 int, col_3 int, col_4 int
+);
+
+-- from citus local to reference - 2
+ALTER TABLE set_on_default_test_referencing ADD CONSTRAINT fkey
+FOREIGN KEY(col_1, col_3) REFERENCES set_on_default_test_referenced(col_1, col_3)
+ON DELETE SET DEFAULT;
+
+DROP TABLE set_on_default_test_referencing, set_on_default_test_referenced;
+
+CREATE TABLE set_on_default_test_referenced(
+    col_1 int, col_2 int, col_3 int, col_4 int,
+    unique (col_1, col_3)
+);
+SELECT citus_add_local_table_to_metadata('set_on_default_test_referenced');
+
+-- from citus local to citus local
+CREATE TABLE set_on_default_test_referencing(
+    col_1 int, col_2 int, col_3 serial, col_4 int,
+    FOREIGN KEY(col_1, col_3)
+    REFERENCES set_on_default_test_referenced(col_1, col_3)
+    ON DELETE SET DEFAULT
+);
+
 -- cleanup at exit
 DROP SCHEMA ref_citus_local_fkeys CASCADE;